Je vais acheter DU pain CHEZ le boucher qui est AU coin de la rue. CHEZ + nom de la personne AU / A + lieu

But whether to use a or de is the tricky part and yes, as you said, a matter of verb. I bought an old text book entirely dedicated to this subject (which should indicate that this indeed is tricky for many people), and sadly it is out of print. I found part one miraculously at a used book store, and part two online. It is possible to find used if you search for it. It is called "Est-ce a ou de? by E. Lasserre. Part one is the Repertoire, des verbes adjectifs et locutions se construisant avec une preposition. Part two is the exercises. Good luck!!